User Authenticate problem

We built a server using Apche + Linux + tomcat3.2 .We use HTTP Basic Authentication technology within HTTP Protocol( that means using HTTP Realm Tag and sends pasword with base64 coding ) . In server side , if the user/password is not correct , we wrote some code showed as following in servlet's service()function res.setHeader("WWW-Authenticate", "BASIC realm=\"Lib adminis trator\""); res.sendError(HttpServletResponse.SC_UNAUTHORIZED); But what's really strange is that in client side , this code doesn't pop out some windows to allow user to input user name /password .the browser is redirect to Tomcat's JSP sample Security/login.jsp that come with Tomcat3.2.1 Is there some explanation for this ?Please tell me why and how to solve this problem ? Thanx in advance ZY